Review fixes for mongo-3.1:javaagent (#17537)

Co-authored-by: otelbot <197425009+otelbot@users.noreply.github.com>
Co-authored-by: Trask Stalnaker <trask.stalnaker@gmail.com>

Author: otelbot[bot]

instrumentation/mongo/mongo-3.1/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/mongo/v3_1/MongoClientInstrumentationModule.java

@@ -69,7 +69,7 @@ public static void injectTraceListener(
           return;
         }
       }
-      builder.addCommandListener(MongoInstrumentationSingletons.LISTENER);
+      builder.addCommandListener(MongoInstrumentationSingletons.getListener());
     }
   }
 }

instrumentation/mongo/mongo-3.1/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/mongo/v3_1/MongoInstrumentationSingletons.java

@@ -21,10 +21,14 @@ public final class MongoInstrumentationSingletons {
           "io.opentelemetry.mongo-3.1",
           DbConfig.isQuerySanitizationEnabled(GlobalOpenTelemetry.get(), "mongo"));
 
-  public static final CommandListener LISTENER = new TracingCommandListener(instrumenter);
+  private static final CommandListener listener = new TracingCommandListener(instrumenter);
 
-  public static boolean isTracingListener(CommandListener listener) {
-    return listener.getClass().getName().equals(LISTENER.getClass().getName());
+  public static CommandListener getListener() {
+    return listener;
+  }
+
+  public static boolean isTracingListener(CommandListener commandListener) {
+    return commandListener.getClass().getName().equals(listener.getClass().getName());
   }
 
   private MongoInstrumentationSingletons() {}